A fluorinated compound is suitably used as a surface treating agent since it has high lubricity, water/oil repellency, etc. By imparting water/oil repellency to a substrate surface, stains will easily be wiped off, and stain removability will be improved.
For example, a touch panel is required to have performance maintained for a long period of time, such that the water/oil repellency will hardly be decreased even after repeatedly rubbed with fingers, and finger prints can easily be removed by wiping.
Among fluorinated compounds, a compound having as a main chain a perfluoropolyether chain in which an ether bond (—O—) is present in the middle of a perfluoroalkyl chain is a compound excellent in the flexibility and is particularly excellent in the fat and oil stain removability.
Use of a fluorinated ether compound having a perfluoropolyether chain as a main chain and having a hydrolyzable silyl group at its terminal, as a surface treating agent such as an antifouling agent, a lubricant or a water/oil repellent, has been known (Patent Documents 1 and 2).
A fluorinated ether compound having a hydrolyzable silyl group at its terminal tends to have favorable durability since the hydrolyzable silyl group is chemically bonded to the surface of a substrate. Example 1 in Patent Document 1 is an Example in which CF3CF2CF2(OCF2CF2CF2)22OCF2CF2CH2OCH2CH═CH2 having an allyl group at its terminal and trichlorosilane are reacted in the presence of a platinum catalyst to produce the following compound (i). It is disclosed that the following compounds (II) and (iii) form as by-products, and their molar ratio is (i)/(ii)/(iii)=85 mol %/2 mol %/13 mol %.CF3CF2CF2(OCF2CF2CF2)22OCF2CF2CH2OCH2CH2CH2Si(OCH3)3  Compound (i)CF3CF2CF2(OCF2CF2CF2)22OCF2CF3  Compound (ii)CF3CF2CF2(OCF2CF2CF2)22OCF2CF2CH2OCH═CHCH3  Compound (iii)
Patent Document 2 discloses an Example in which RF1O(CF2CF2O)aCF2CH2OH and Cl—CH2CH2CH2—SiLpR3-p are reacted in the presence of sodium hydride to obtain a fluorinated ether composition containing as the main component RF1O(CF2CF2O)aCF2CH2OCH2CH2CH2—SiLpR3-p (paragraphs [0052] and [0053]).
Since a compound having an allyl group at its terminal is not used as the material, a by-product having —OCH2CH(SiLnR3-n)CH3 at its terminal will not form.